In 1899, Alexander Graham Bell, famous for inventing the telephone, began experimenting with kites in search of insights into the possibility of powered flight.

Inspired by the box kite designs of Australian Laurence Hargrave, Bell began multiplying the lift-providing cells, creating compound structures of multiple kites.

The basic problem of creating flying objects is that as a body’s surface area is squared, its weight is cubed, limiting the maximum size and lifting capability.

Over the course of years experimenting at his Nova Scotia laboratory, Bell discovered that a tetrahedron — a three-dimensional prism of four triangular sides — could be useful.

May 16, 1902

A kite with four triangular cells in flight.

Image: National Geographic Creative/Corbis

Bell built tetrahedral cells with 10-inch spruce rods, with two sides of each pyramidal polygon covered in crimson silk, weighing about an ounce in total.

Creating compound assemblies of these pyramid-shaped cells, with shared joints and spars, allowed Bell to scale up his designs without increasing the weight-to-surface area ratio.

Bell’s largest tetrahedral design, the “Cygnet,” was composed of 3,393 cells. It successfully flew and carried a human passenger when towed behind a steamship, but was destroyed on landing.

That passenger, U.S. Army Lt. Thomas E. Selfridge, would later become the first person to die in a powered airplane flight as a passenger on a Wright Brothers invention.

May 17, 1902

A kite with six triangular cells in flight.

Image: National Geographic Creative/Corbis

June 13, 1902

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May 29, 1902

Bell's assistants attempt to launch a multicellular kite.

Image: National Geographic Creative/Corbis

June 30, 1902

A complex multicellular kite.

Image: National Geographic Creative/Corbis

The tetrahedral principle enables us to construct out of light materials solid frameworks of almost any desired form, and the resulting structures are admirably adapted for the support of aero-surfaces of any desired kind, size, or shape.

Alexander Graham Bell, National Geographic, 1903

June 20, 1902

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Oct. 4, 1902

A multicelled triangular kite.

Image: National Geographic Creative/Corbis

Aug. 23, 1902

A kite composed of three six-celled wheels.

Image: National Geographic Creative/Corbis

August 1902

A kite with three six-celled wheels in flight.

Image: National Geographic Creative/Corbis

June 24, 1902

An assistant holds a multicellular kite.

Image: National Geographic Creative/Corbis

1902

An assistant with a tetrahedral framework.

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Nov. 18, 1902

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Oct. 2, 1902

Assistants build a massive tetrahedral kite.

Image: National Geographic Creative/Corbis

1904

Bell poses with some of his tetrahedral kites.

Image: Corbis

Dec. 19, 1905

One of Bell's tetrahedral kites, dubbed "Oionos."

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Dec. 16, 1905

Assistants hoist a kite dubbed "The Frost King."

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Dec. 16, 1905

Bell's assistants carry "The Frost King."

Image: National Geographic Creative/Corbis

Aug. 9, 1906

A tetrahedral kite is towed on the water.

Image: National Geographic Creative/Corbis

July 7, 1908

Alexander Graham Bell (right) and his assistants observe the flight of a circular tetrahedral kite.